Adhesively- and solder-bonded capacitive filter feedthrough for implantable medical devices

ABSTRACT

A capacitive filter feedthrough assembly and method of making same are disclosed for shielding an implantable medical device such as pacemaker or defibrillator from electromagnetic interference or noise. A ferrule is adapted for mounting onto a conductive device housing by welding, soldering, brazing or gluing, and supports a terminal pin for feedthrough passage to a housing interior. A capacitive filter is mounted at the inboard side of a device housing, with capacitive filter electrode plate sets coupled respectively to the housing and the terminal pin by an electrically conductive combination of adhesive, brazing and soldering. In one embodiment of the invention, multiple capacitive filters are provided in an array within a common base structure, where each capacitive filter is associated with a respective terminal pin.

This application is a Continuation-in-Part of application Ser. No.08/852,198 filed May 6, 1997 now U.S. Pat. No. 5,870,272.

FIELD OF THE INVENTION

This invention relates to electrical feedthroughs of improved design andto their method of fabrication.

BACKGROUND OF THE INVENTION

Electrical feedthroughs serve the purpose of providing an electricalcircuit path extending from the interior of a hermetically sealedcontainer to an external point outside the container. A conductive pathis provided through the feedthrough by a conductor pin which iselectrically insulated from the container. Many such feedthroughs areknown in the art which provide the electrical path and seal theelectrical container from its ambient environment. Such feedthroughstypically include a ferrule, the conductor pin or lead and a hermeticglass or ceramic seal which supports the pin within the ferrule. Suchfeedthroughs are typically used in electrical medical devices such asimplantable pulse generators (IPGs). It has recently been discoveredthat such electrical devices can, under some circumstances, besusceptible to electromagnetic interference (EMI). At certainfrequencies for example, EMI can inhibit pacing in an IPG. This problemhas been addressed by incorporating a capacitor structure within thefeedthrough ferrule, thus shunting any EMI at the entrance to the IPGfor high frequencies. This has been accomplished with the aforementionedcapacitor device by combining it with the feedthrough and incorporatingit directly into the feedthrough ferrule. Typically, the capacitorelectrically contacts the pin lead and the ferrule.

Some of the more popular materials employed to form the pin lead includetantalum and niobium. Unfortunately, tantalum and niobium aresusceptible to oxide growth which can, depending on its extent, act asan insulator instead of a conductor over the surface of the pin lead.During fabrication of a feedthrough and capacitor combination, the pinis subjected to one or more heat treatments which can encourageoxidation, affecting the conductivity of the pin lead and its ability tomake good electrical connections between other elements including thecapacitor and so forth.

Many different insulator structures and related mounting methods areknown in the art for use in medical devices wherein the insulatorstructure also provides a hermetic seal to prevent entry of body fluidsinto the housing of the medical device. However, the feedthroughterminal pins are connected to one or more lead wires which effectivelyact as an antenna and thus tend to collect stray or electromagneticinterference (EMI) signals for transmission to the interior of themedical device. In some prior art devices, ceramic chip capacitors areadded to the internal electronics to filter and thus control the effectsof such interference signals. This internal, so-called "on-board"filtering technique has potentially serious disadvantages due tointrinsic parasitic resonances of the chip capacitors and EMI radiationentering the interior of the device housing.

In another and normally preferred approach, a filter capacitor iscombined directly with a terminal pin assembly to decouple interferencesignals to the housing of the medical device. In a typical construction,a coaxial feedthrough filter capacitor is connected to a feedthroughassembly to suppress and decouple undesired interference or noisetransmission along a terminal pin.

So-called discoidal capacitors having two sets of electrode platesembedded in spaced relation within an insulative substrate or basetypically form a ceramic monolith in such capacitors. One set of theelectrode plates is electrically connected at an inner diameter surfaceof the discoidal structure to the conductive terminal pin utilized topass the desired electrical signal or signals. The other or second setof electrode plates is coupled at an outer diameter surface of thediscoidal capacitor to a cylindrical ferrule of conductive material,wherein the ferrule is electrically connected in turn to the conductivehousing or case of the electronic instrument.

In operation, the discoidal capacitor permits passage of relatively lowfrequency electrical signals along the terminal pin, while shunting andshielding undesired interference signals of typically high frequency tothe conductive housing. Feedthrough capacitors of this general type arecommonly employed in implantable pacemakers, defibrillators and thelike, wherein a device housing is constructed from a conductivebiocompatible metal such as titanium and is electrically coupled to thefeedthrough filter capacitor. The filter capacitor and terminal pinassembly prevent interference signals from entering the interior of thedevice housing, where such interference signals might otherwiseadversely affect a desired function such as pacing or defibrillating.

In the past, feedthrough filter capacitors for heart pacemakers and thelike have typically been constructed by preassembly of the discoidalcapacitor with a terminal pin subassembly which includes the conductiveterminal pin and ferrule. More specifically, the terminal pinsubassembly is prefabricated to include one or more conductive terminalpins supported within the conductive ferrule by means of a hermeticallysealed insulator ring or bead. See, for example, the terminal pinsubassemblies disclosed in U.S. Pat. Nos. 3,920,888, 4,152,540;4,421,947; and 4,424,5511. The terminal pin subassembly thus defines asmall annular space or gap disposed radially between the inner terminalpin and the outer ferrule. A small discoidal capacitor of appropriatesize and shape is then installed into this annular space or gap, inconductive relation with the terminal pin and ferrule, by means ofsoldering, conductive adhesive, etc. The thus-constructed feedthroughcapacitor assembly is then mounted within an opening in the pacemakerhousing, with the conductive ferrule in electrical and hermeticallysealed relation in respect of the housing, shield or container of themedical device.

Although feedthrough filter capacitor assemblies of the type describedabove have performed in a generally satisfactory manner, the manufactureand installation of such filter capacitor assemblies has been relativelycostly and difficult. For example, installation of the discoidalcapacitor into the small annular space between the terminal pin andferrule can be a difficult and complex multi-step procedure to ensureformation of reliable, high quality electrical connections. Moreover,installation of the capacitor at this location inherently limits thecapacitor to a small size and thus also limits the capacitance thereof.Similarly, subsequent attachment of the conductive ferrule to thepacemaker housing, typically by welding or brazing processes or thelike, can expose the fragile ceramic discoidal capacitor to temperaturevariations sufficient to create the risk of capacitor cracking andfailure.

There exists, therefore, a significant need for improvements infeedthrough filter capacitor assemblies of the type used, for example,in implantable medical devices such as heart pacemakers and the like,wherein the filter capacitor is designed for relatively simplified andeconomical, yet highly reliable, installation. In addition, there existsa need for an improved feedthrough assembly having a discoidal capacitorwhich can be designed to provide a significantly increased capacitancefor improved filtering. The present invention fulfills these needs andprovides further advantages.

Disclosures relating to implantable medical devices, feedthroughs andcapacitive filtering of EMI include the patents listed below in Table 1.

                  TABLE 1                                                         ______________________________________                                        Prior Art Patents                                                             ______________________________________                                        U.S. Patents                                                                  1,180,614                                                                              4/1916     Simpson      428/662                                      2,756,375                                                                              7/1956     Peck         361/302                                      3,266,121                                                                              8/1966     Rayburn      29/25.42                                     3,235,939                                                                              2/1966     Rodriguez et al.                                                                           29/25.42                                     3,304,362                                                                              2/1967     August       174/50.61                                    3,538,464                                                                              11/1970    Walsh        361/302 X                                    3,624,460                                                                              11/1971    Correll      29/25.03 X                                   3,844,921                                                                              10/1974    Benedict     204/196                                      3,920,888                                                                              11/1975    Barr         174/152GM                                    4,010,759                                                                              3/1977     Boer         174/152GM X                                  4,015,175                                                                              3/1977     Kendall et al.                                                                             361/313                                      4,041,587                                                                              8/1977     Kraus        29/25.42                                     4,083,022                                                                              4/1978     Nijman       333/185                                      4,107,762                                                                              8/1978     Shirn et al. 29/25.04 X                                   4,148,003                                                                              4/1979     Colburn et al.                                                                             361/302                                      4,152,540                                                                              5/1979     Duncan et al.                                                                              174/152GM                                    4,168,351                                                                              9/1979     Taylor       333/182                                      4,220,813                                                                              9/1980     Kyle         174/152GM                                    4,247,881                                                                              1/1981     Coleman      361/302                                      4,314,213                                                                              2/1982     Wakino       361/302                                      4,352,951                                                                              10/1982    Kyle         174/152GM                                    4,362,792                                                                              12/1982    Bowsky et al.                                                                              174/152GM                                    4,421,947                                                                              12/1983    Kyle         174/152GM                                    4,424,551                                                                              1/1984     Stevenson    361/302                                      4,456,786                                                                              6/1984     Kyle         174/152GM                                    4,556,613                                                                              12/1985    Taylor et al.                                                                              429/101                                      4,683,516                                                                              7/1987     Miller       361/328                                      4,737,601                                                                              4/1988     Gartzke      174/152GM                                    4,741,710                                                                              5/1988     Hogan et al. 333/185                                      4,791,391                                                                              12/1988    Linnell      361/302                                      4,934,366                                                                              9/1989     Truex et al. 128/419                                      5,032,692                                                                              7/1991     DeVolder     361/30.2                                     5,070,605                                                                              12/1991    Daglow et al.                                                                              29/842                                       5,104,755                                                                              4/1992     Taylor et al.                                                                              174/50.61                                    5,144,946                                                                              9/1992     Weinberg et al.                                                                            178/419                                      5,333,095                                                                              7/1994     Stevenson et al.                                                                           29/25.42 X                                   5,406,444                                                                              4/1995     Seifried     361/302                                      5,440,447                                                                              8/1995     Shipman et al.                                                                             361/302                                      5,531,003                                                                              7/1996     Seifried     29/25.42                                     5,535,097                                                                              7/1996     Ruben        361/736                                      Foreign Patents                                                               2815118  10/1978    Fed. Rep. of Ger.                                                                          361/302                                      0331959  9/1989     E.P.O.                                                    892492   2/1981     U.S.S.R.     29/25.42                                     ______________________________________                                    

As those of ordinary skill in the art will appreciate readily uponreading the Summary of the Invention, Detailed Description of thePreferred Embodiments and Claims set forth below, many of the devicesand methods disclosed in the patents of Table 1 may be modifiedadvantageously by using the teachings of the present invention.

SUMMARY OF THE INVENTION

The present invention has certain objects. That is, the presentinvention provides solutions to at least some of the problems existingin the prior art respecting capacitive filters in feedthroughassemblies.

The present invention provides solutions to at least some of theproblems associated with conventional capacitive filter feedthroughassembly designs where a discoidal capacitor is placed within ferrulewalls, such as in U.S. Pat. Nos. 4,424,551 and 5,333,095. At least someaspects of known capacitive filter feedthrough assemblies may becharacterized generally as:

(a) involving difficult to implement conductive epoxy placement steps;

(b) having high electrical resistances at refractory metal interfacesowing to the presence of conductive epoxy and undesirable metal oxides;

(c) exhibiting poor or variable electrical performance in respect of EMIsignal attenuation;

(d) requiring multiple labor intensive manufacturing processing steps;

(e) having through pins which cannot be wire bonded to, or are difficultto wire bond to;

(f) exhibiting electrical shorts owing to uncontrolled or inaccurateepoxy placement;

(g) having capacitors crack owing to differing thermal expansioncoefficients of the conductive can, the capacitor or the electricallyconductive epoxy commonly employed to attach the capacitor to a ferruleor container;

(h) providing no opportunity for visual inspection of the feedthroughassembly once installed in the device;

(I) not permitting the use of registration or centering elements duringthe manufacturing process, or

(j) exhibiting poor mechanical joint strength.

The present invention provides solutions to at least some of theproblems associated with conventional capacitive filter feedthroughassembly designs where a capacitor is placed to one side of afeedthrough such as in U.S. Pat. No. 5,333,095. Capacitive filterfeedthrough assemblies disclosed in the '095 patent may be characterizedgenerally as:

(a) not permitting the use of registrations or centering elements;

(b) having through pins which cannot be wire bonded to, or are difficultto wire bond to;

(c) having capacitors crack owing to differing thermal expansioncoefficients of the conductive can and the capacitor;

(d) exhibiting poor mechanical joint strength.

The present invention provides solutions to at least some of theproblems associated with conventional capacitive filter feedthroughassembly designs where solder is employed to connect a capacitor to afeedthrough. Capacitive filter feedthrough assemblies of the typeemploying solder to connect capacitors to feedthroughs are generallycharacterized in the use of flux to solder a capacitor to a feedthrough.The use of flux increases the number of manufacturing steps required tomake a device because of the requisite cleaning attending the use offlux. Cleaning is required when using flux because otherwise degradationof the hermetic seal can occur due to the presence of moisture andcorrosive ionic components in flux material.

Some embodiments of the present invention provide certain advantageswhich include, but are not limited to:

(a) permitting the attachment of a capacitive filter to gold brazing;

(b) increasing the electrical conductivity between a capacitive filterand a feedthrough;

(c) increasing the EMI filtering capability provided for an implantablemedical device;

(d) eliminating the presence of electrically resistive metal oxidesbetween a capacitive filter and a shield or feedthrough;

(e) requiring only one method for connecting a capacitive filter to apin or ferrule;

(f) eliminating secondary manufacturing process steps such as epoxyapplication or additional soldering steps;

(g) reducing manufacturing costs;

(h) reducing implantable medical device costs;

(I) enclosing a capacitive filter at least partially in a ferrule tothereby provide additional mechanical support to the filter;

(j) eliminating secondary cleaning steps associated with soldering;

(k) permitting the use of a capacitive filter having higher capacitancesthan chip capacitors, and therefore providing enhanced EMI filteringcapability;

(l) providing a protruding upper capacitive filter wire bond padsuitable for wire bonding thereto;

(m) preventing chipping or abrasion of a capacitive filter due topass-through pin bending, and

(n) permitting the use of sputtered capacitors, and

(o) permitting the use of low temperature solders having increasedductility and enhanced corrosion resistance.

Some embodiments of the present invention have certain features,including, but not limited to:

(a) a capacitive filter that is at least partially disposed within orsurrounded by first sidewalls forming a first aperture in a ferrule;

(b) a capacitive filter that is surface mounted or otherwise disposedatop a ferrule, the filter not being disposed within the first aperture,or not being surrounded by the first sidewalls;

(c) a pin having an upper portion, the upper portion extending upwardlyinto a second aperture in an insulator, the pin being electrically andmechanically connected to a contact pad extending downwardly into athird aperture of the capacitive filter;

(d) a pin, the upper portion thereof extending through or substantiallythrough the second aperture, the upper portion optionally extendingthrough or substantially through the first aperture;

(e) a feedthrough assembly having no contact pad disposed within thefirst ferrule, where electrical and mechanical connection of internalcircuitry to the pin of the assembly is accomplished by attaching anelectrical conductor in or to the third aperture of the capacitivefilter, the filter being disposed within or atop the first aperture;

(f) inner braze joints, intermediate braze joints, and/or outer brazejoints formed of: (I) pure gold; (ii) gold alloys comprising gold and atleast one of titanium, niobium, vanadium, nickel, molybdenum, platinum,palladium, ruthenium, silver, rhodium, osmium, iridium, and alloys,mixtures and thereof; (iii) copper-silver alloys, includingcopper-silver eutectic alloys, comprising copper and silver andoptionally at least one of indium, titanium, tin, gallium, palladium,platinum, and alloys, mixtures and combinations thereof; and (iv)silver-palladium-gallium alloys;

(g) an inner solder joint and/or an outer solder joint electrically andmechanically connected to an inner braze joint and/or an outer brazejoint, and/or an inner adhesive joint or an outer adhesive joint, thesolder joints being formed of: (i) indium only; (ii) lead only; (iii)silver only; (iv) tin only; (v) indium-silver alloys; (vi) indium-tinalloys; (vii) tin-lead alloys; (viii) tin-silver alloys; (ix)indium-lead-silver alloys; (x) tin-lead-silver alloys, (xi) alloys,mixtures and combinations of (I) through (x); and (xii) gold-containingsolders such as: (1) gold-tin alloys; (2) gold-silicon alloys; (3)gold-germanium alloys; (4) gold-indium alloys, and alloys, mixtures andcombinations of (1) through (4); and

(h) inner adhesive joints and/or outer adhesive joints electrically andmechanically connected to an inner braze joint and/or an outer brazejoint, and/or to an inner solder joint and/or an outer solder joint, theadhesive joints being formed of a suitable, preferably epoxy-based,material, and

(i) at least one capacitive filter having first and second electricalterminals connected electrically and mechanically through braze andadhesive joints, respectively, and optionally through other componentsto circuitry internal to an implantable medical device and to theimplantable medical device case or shield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of one embodiment of a uni-polarfeedthrough assembly of the present invention;

FIG. 2 shows an exploded, perspective view of the uni-polar feedthroughassembly of FIG. 1;

FIG. 3 shows a cross-sectional view of one embodiment of a multi-polarfeedthrough assembly of the present invention;

FIG. 4 shows an enlarged view of a portion of the multi-polarfeedthrough assembly of FIG. 3;

FIG. 5 shows an exploded perspective view of portions of the multi-polarfeedthrough assembly of FIGS. 3 and 4;

FIG. 6 shows a perspective, cut-away view of the internal components ofan implantable medical device of the present invention;

FIG. 7 shows a cross-sectional view of the implantable medical device ofFIG. 6;

FIG. 8 shows a flow chart of one method of the present invention;

FIG. 9 shows graphs of EMI insertion loss data obtained with capacitivefilter feedthroughs of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the claims and specification hereof, the adjective "upper" refers tothose portions of feedthrough assembly 5 having contact pad 60propinquant thereto, the adjective "lower" refers to those portions offeedthrough assembly 5 having pin 30 propinquant thereto, the adjective"inner" refers to those portions of feedthrough assembly 5 havingcentral vertical axis 100 of pin 30 propinquant thereto, and theadjective "outer" refers to those portions of feedthrough assembly 5having outer surface 80 of capacitive filter 50 propinquant thereto.

We refer to U.S. Pat. No. 4,678,868 to Kraska et al., which disclosesbrazing techniques suitable for use in feedthrough assemblies inimplantable medical devices, at least some of which techniques may beadapted for use in the present invention.

FIG. 1 shows a cross-sectional view of one embodiment of a uni-polarfeedthrough assembly 5 of the present invention after being subjected tothe brazing and adhesive-bonding steps of the present invention. FIG. 2shows an exploded, perspective view of the uni-polar feedthroughassembly of FIG. 1.

Electrically conductive ferrule 10 of FIGS. 1 and 2 is preferably weldedto shield or container 20 of hermetically sealed implantable medicaldevice 70, and has first aperture 12 disposed therethrough formed byfirst sidewalls 14. Electrically insulative insulator 25 is disposedwithin first aperture 12, provides electrical insulation betweenelectrically conductive feedthrough pin 30 and ferrule 10, and hassecond aperture 27 disposed therethrough formed by second sidewalls 29.

Ferrule 10 is typically laser welded to shield or container 20, and maybe formed of niobium, titanium, titanium alloys such as titanium-6AI-4Vor titanium-vanadium, platinum, molybdenum, zirconium, tantalum,vanadium, tungsten, iridium, rhodium, rhenium, osmium, ruthenium,palladium, silver, and alloys, mixtures and combinations thereof.Ferrule 10 may be welded by other means to shield or container 20, oreven soldered or glued thereto.

Upper portion 32 of electrically conductive pin 30 is disposed within ormay extend at least partially into second aperture 27. Lower portion 34of pin 30 is generally connected to electrical circuitry, connectors ora connector block external to container 20 of device 70, but mayalternatively be connected directly to a connector on a medical lead. Inone embodiment of the present invention, upper portion 32 of pin 30extends upwardly into second aperture 27, and is electrically andmechanically connected by inner braze joint 65 and inner adhesive joint55 to contact pad 60, where contact pad 60 extends downwardly into thirdaperture 35 of capacitive filter 50.

In another embodiment of the present invention, upper portion 32 of pin30 extends through or substantially through second aperture 27, and mayoptionally extend through or substantially through first aperture 12.Upper portion 32 of pin 30 may also be connected directly to anelectrical conductor attached to internal circuitry, with no contact pad60 being disposed in third aperture 35.

Pin 30 may be formed of niobium, titanium, titanium alloys such astitanium-6AI-4V or titanium-vanadium, platinum, molybdenum, zirconium,tantalum, vanadium, tungsten, iridium, rhodium, rhenium, osmium,ruthenium, palladium, silver, and alloys, mixtures and combinationsthereof.

Electrically conductive intermediate braze joint 15 most preferablyprovides an hermetic braze joint and seal between ferrule 10 andinsulator 25, and is disposed between at least outer insulator surface90 and first sidewalls 14 of first aperture 12.

Insulator 25 is most preferably formed of alumina (or aluminum oxide),but may be formed of any suitable electrically insulative,ceramic-containing material comprising, for example, sapphire orzirconium oxide. Under certain circumstances, inner insulator surface 85and outer insulator surface 90 must have a suitable metal or alloydisposed thereon to permit insulator 25 to be brazed to pin 30 or toferrule 10.

In a preferred embodiment of the present invention, where pure gold isemployed to form inner and intermediate braze joints 65 and 15, a 25,000Angstrom thick layer of niobium is sputtered onto surfaces 85 and 90 byvacuum deposition using a Model No. 2400 PERKIN-ELMER® sputteringsystem. The niobium layer is most preferably between about 15,000 andabout 32,000 Angstroms thick. Metals other than niobium may be sputteredon surfaces 85 and 90, such as titanium or molybdenum. If metals suchas: (i) gold alloys comprising gold and at least one of titanium,niobium, vanadium, nickel, molybdenum, platinum, palladium, ruthenium,silver, rhodium, osmium, iridium, and alloys, mixtures and thereof; (ii)copper-silver alloys, including copper-silver eutectic alloys,comprising copper and silver and optionally at least one of indium,titanium, tin, gallium, palladium, platinum; or (iii) alloys, mixturesor combinations of (i) or (ii) are employed, then metallization ofsurfaces 85 and 90 may not be required.

Optional electrically conductive outer braze joint 40 provides aplatform for the attachment of outer adhesive joint 45 and/or outersolder joint 45 thereto. In preferred embodiments of the presentinvention, braze joint 40 is disposed between sidewalls 14 of firstaperture 12 and outer surface 80 of capacitive filter 50. In otherpreferred embodiments of the present invention, outer braze 40 isdisposed atop ferrule 10 along the top peripheral surface thereof. Outerbraze joint 40 need not, but may, provide a hermetic seal.

Electrically conductive outer solder joint 45, may be disposed betweenferrule 10 and outer braze joint 40 on the one hand, and a secondterminal or electrode of capacitive filter 50 on the other hand, toprovide a solder joint therebetween. Outer solder seal 45 need not, butmay, provide a hermetic seal. Outer solder joint 45 may permit a secondterminal or electrode of capacitor 50 to be mechanically andelectrically affixed by solderable means to ferrule 10 through outerbraze joint 40.

Electrically conductive inner solder joint 55 may be disposed in thirdaperture or passageway 35 of capacitor 50 between contact pad 60 andinner braze joint 65, to provide a solder joint therebetween. Innersolder seal 55 need not, but may, provide a hermetic seal. Inner solderjoint 55 permits a first terminal or electrode of capacitor 50 to bemechanically and electrically affixed by solderable means to ferrule 10through inner braze joint 65.

Electrically conductive outer adhesive joint 45 is preferably disposedbetween ferrule 10 and outer braze joint 40 on the one hand, and asecond terminal or electrode of capacitive filter 50 on the other hand,and provides an adhesive joint therebetween. Outer adhesive joint 45need not, but may, provide a hermetic seal. Outer adhesive joint 45 maybe employed to permit a second terminal or electrode of capacitor 50 tobe mechanically and electrically affixed by adhesive means to ferrule 10through outer braze joint 40.

Alternatively, and in a manner not shown in the Figures, outer adhesivejoint 45 may be connected to a second terminal or outer surface 80 offilter 50 as follows. Insulator 25 may have a wider outer diameter andferrule 10 may have a lower profile (or lower or non-existent topportion 93) than those shown in FIGS. 1 and 2, such that the secondterminal or outer surface 80 of filter 50 may engage, through outeradhesive joint 45, intermediate braze joint 15. In such a configuration,top portion 93 of ferrule 10 may be eliminated or shortened in height,and outer braze joint 40 may be eliminated altogether. In anotherembodiment of the present invention not shown in the Figures, outeradhesive joint 45 and/or outer braze joint 40 may be replaced with outersolder joint 45 of the present invention (some suitable compositions ofwhich are more fully described below).

Inner adhesive joint 55 and outer adhesive joint 45 are most preferablyformed of the same adhesive material, but may less preferably be formedof different adhesive materials. In preferred embodiments of the presentinvention, outer adhesive joint 45 and inner adhesive joint 55 areformed of ABLEBOND® 8700 electrically conductive silver-filled epoxyadhesive provided by ABLESTIK LABORATORIES of Rancho Dominguez, Calif.Other suitable electrically conductive glue- or epoxy-based adhesivesand other suitable materials may also be employed in the presentinvention to form joints 55 or 45. Such materials include gold-orcopper-filled epoxies, carbon- or graphite-filled epoxies or evenelectrically conductive plastics acting effectively as adhesive jointsafter their application and upon cooling, such as at least some of theelectrically conductive plastics or polymers disclosed in U.S. Pat. No.5,685,632 to Schaller et al. for "Electrically Conductive Plastic LightSource."

Inner braze joint 65 provides a braze joint and seal between insulator25 and pin 30, and further forms a portion of an electrically conductivepathway extending between pin 30 and contact pad 60, the pathwaycomprising, but not necessarily limited to, pin 30, inner braze joint65, inner solder joint 55 and contact pad 60. Inner braze joint 65 isdisposed atop or at least partially surrounds upper portion 32 of pin30. Inner braze joint 65 is also disposed between at least a portion ofupper portion 32 of pin 30 and second sidewalls 85 (or inner insulatorsurface 85) of second aperture 27. In another embodiment of the presentinvention inner adhesive joint 55 replaces or augments inner solderjoint 55.

Inner braze joint 65, intermediate braze joint 15 and outer braze joint40 are most preferably formed of the same metal or alloy, but may lesspreferably be formed of different metals or alloys. Braze joints 65, 15and 40 of the present invention are most preferably formed of 99.9% orpurer gold, but may also be formed of: (a) gold alloys comprising goldand at least one of titanium, niobium, vanadium, nickel, molybdenum,platinum, palladium, ruthenium, silver, rhodium, osmium, indium, andalloys, mixtures and thereof; (b) copper-silver alloys, includingcopper-silver eutectic alloys, comprising copper and silver andoptionally at least one of indium, titanium, tin, gallium, palladium,platinum, and alloys, mixtures and combinations thereof; and (c)silver-palladium-gallium alloys.

Inner solder joint 55 and outer solder joint 45 most preferably comprisethe same or similar metals or alloys, but may less preferably be formedof different or dissimilar metals or alloys. In preferred embodiments ofthe present invention, inner solder joint 55 and outer solder joint 45are formed of an indium-lead solder, and most preferably an indium-leadsolder comprising, by weight percent, 70% indium and 30% lead. Othermetals or alloys for forming inner solder joint 55 and outer solderjoint 45 of the present invention include: (a) indium only; (b) leadonly; (c) silver only; (d) tin only; (e) indium-silver alloys; (f)indium-tin alloys; (g) tin-lead alloys; (h) tin-silver alloys; (h)indium-lead-silver alloys; (I) tin-lead-silver alloys, and other alloys,mixtures and combinations thereof. Still other metals or alloys forforming inner solder joint 55 and outer solder joint 45 of the presentinvention include gold-containing solders such as: (a) gold-tin alloys;(b) gold-silicon alloys; (c) gold-germanium alloys; gold-indium alloys,and alloys, mixtures and combinations thereof.

In one embodiment of the present invention, contact pad 60 iselectrically connected to internal circuitry disposed within containeror shield 20 of hermetically sealed implantable medical device 70, andis also electrically and mechanically connected to pin 30 through innerbraze joint 65 and inner solder joint 55. Electrical connection frominternal circuitry to contact pad 60 may be established by wire bonding,soldering, welding, laser welding, brazing, gluing or other suitablemeans.

In another embodiment of the present invention, contact pad 60 iselectrically connected to internal circuitry disposed within containeror shield 20 of hermetically sealed implantable medical device 70, andis also electrically and mechanically connected to pin 30 through innerbraze joint 65 and inner solder joint 55 and/or inner adhesive joint 55.Electrical connection from internal circuitry to contact pad 60 may beestablished by wire bonding, soldering, welding, laser welding, brazing,gluing or other suitable means.

In still another embodiment of the present invention, no contact pad 60is disposed within third aperture 35, and electrical and mechanicalconnection to internal circuitry of device 70 is accomplished byattaching an electrical conductor to inner solder joint 55 or inneradhesive joint 55, or directly to inner braze joint 65, through thirdaperture 35 by appropriate wire bonding, soldering, welding, laserwelding, brazing, gluing or other suitable electrically conductiveattachment means.

Contact pad 60 is most preferably formed of KOVAR® (aniron-nickel-cobalt alloy) having electroplated layers of first nickeland then gold disposed on the surface thereof. Contact pad 60 may alsobe formed of: (a) brass first plated with nickel and then gold; (b) puregold; (c) suitable gold alloy plated with gold; (d) nickel plated withgold; (e) suitable nickel alloy plated with gold, and (f) pure copper orcopper alloy first plated with nickel and then gold. Contact pad 60 mustbe electrically conductive and have a melting temperature exceeding themelting temperature of the solder employed to form inner adhesive joint57 or outer adhesive joint 47. Additionally, the metal disposed on theouter surface of contact pad 60 must be compatible with the adhesiveemployed to form inner adhesive joint 55 and/or outer adhesive joint 45and/or the solder employed to form outer solder joint 45 and/or innersolder joint 55.

Ceramic-containing capacitive filter 50 attenuates and filters EMI toprevent the passage or propagation thereof into the interior of shieldor container 20. Filter 50 has a third aperture or pathway 35 disposedthrough a portion thereof for electrical and mechanical connection ofcontact pad 60 to inner adhesive joint 57. Capacitive filter 50 is mostpreferably disposed at least partially in first aperture 12 such thatferrule 10 imparts additional mechanical integrity to the mechanicalconnection between filter 50 and ferrule 10. Alternatively, capacitivefilter 50 is disposed outside first aperture 12 in surface mount fashionsuch that first sidewalls 14 do not at least partially surround outercapacitive filter surface 80, or such that capacitive filter 50 isdisposed atop ferrule 10.

In such alternative embodiments of the present invention, however, outeradhesive joint 55 and/or outer solder joint 45 may provide a mechanicaland electrical bridge between sidewalls 14 of first aperture 12 offerrule 10 (or intermediate braze joint 15) and the second terminal orelectrode of capacitive filter 50 or outer capacitive filter surface 80.In another embodiment of the present invention, outer adhesive joint 45or outer solder joint 45 provide a mechanical and electrical bridgebetween optional outer braze joint 40 (or intermediate braze joint 15)and the second terminal or electrode of capacitive filter 50 or outercapacitive filter surface 80.

In preferred embodiments of the present invention, capacitive filter 50is a discoidal multi-layer ceramic capacitor having a doughnut-likeshape and a central cylindrically-shaped aperture 35 disposed throughthe center thereof. Capacitive filters forming discoidal multi-layerceramic capacitors finding particularly efficacious application in thepresent invention are manufactured by AVX CORPORATION of Myrtle Beach,S.C., MAXWELL LABORATORIES of Carson City, Nevada, CERAMIC DEVICE, INC.of Wenatchee, Wash., and SPECTRUM CONTROL, INC. of Erie, Pa.

Capacitive filters 50 comprising barium titanate have been discovered toprovide particularly good results in the present invention. Examples ofsuitable barium titanate formulations or types for making capacitivefilter 50 include, but are not limited to, X7R, Z5U and otherformulations. Other types of ceramic capacitors may be employed forcapacitive filter 50 of the present invention, such as single-layercapacitors, rectangular capacitors, square capacitors, ellipticalcapacitors, oval capacitors and the like.

In a preferred embodiment of the present invention, capacitive filter 50is a discoidal multi-layer ceramic capacitor having silver thick films,silver-palladium alloy thick films, or silver-platinum alloy thick filmsdisposed on inner capacitive filter surface 75 and outer capacitivefilter surface 80. Such thick films are typically applied by thecapacitive filter manufacturer before shipment. Inner capacitive filtersurface 75 forms a first electrical terminal or contact of capacitivefilter 50.

Outer capacitive filter surface 80 forms a second electrical terminal orcontact of capacitive filter 50. When outer capacitive filter surface 80is electrically connected to shield or container 20 and inner capacitivefilter surface is electrically connected to circuitry or connectorsexternal to container 20 of implantable medical device 70 throughcontact pad 60, capacitive filter 50 is connected in parallel withsignals entering device 70, and thereby provides its EMI filteringcapability.

Optionally, two more metal layers may be disposed on inner and outersurfaces 75 and 80 having silver thick films, silver-palladium alloythick films, or silver-platinum alloy thick films disposed thereon topermit attachment of capacitive filter 50 to outer adhesive joint 47and/or outer solder joint 45 on the one hand, and inner adhesive joint57 and/or inner solder joint 55 on the other hand. First layers ofnickel are preferably sputtered onto the thick films overlying innersurface 75 and outer surface 80. Next, second layers of gold arepreferably sputtered onto the previously deposited nickel layers.

The gold layers provide a means for adhesively attaching capacitivefilter 50 to inner adhesive joint 57 and/or inner solder joint 55 on theone hand, and outer adhesive joint 47 and/or outer solder joint 45 onthe other hand. Metals and alloys other than pure nickel may be employedfor forming the first layers. Pure gold is preferred for forming thesecond layers, but gold of varying purities may less preferably beemployed for forming the second layers.

In another embodiment of the present invention, gold, nickel, titanium,titanium-tungsten alloys, tungsten or molybdenum metal layers may besputtered directly onto inner surface 75 or outer surface 80, with nothick films being disposed thereon.

In the sputtering step of the present invention, a DC magnetronsputtering technique is preferred, but RF sputtering techniques may lesspreferably be employed. A DC magnetron machine that may find applicationin the present invention is an Model 2011 DC magnetron sputtering devicemanufactured by ADVANCED ENERGY of Fort Collins Colo. A preferredthickness for second layers formed of gold is about 10,000 Angstroms. Apreferred thickness for first layers formed of nickel is about 25,000Angstroms.

FIG. 3 shows a cross-sectional view of one embodiment of multi-polarfeedthrough assembly 5 of the present invention after being subjected tothe adhesive application and brazing steps of the present invention.FIG. 4 shows an enlarged view of a portion of multi-polar feedthroughassembly 5 of FIG. 3. FIG. 5 shows an exploded perspective view ofportions of multi-polar feedthrough assembly 5 of FIGS. 3 and 4.

In FIGS. 3, 4 and 5 a plurality of insulators 25, feedthrough pins 30,capacitive filters 50, contact pads 60 and other components are disposeddirectly in ferrule 10. Spacers or washers 95 in FIGS. 3 and 4 areoptional, and need not, but may, be included in assembly 5 if the headportion of pin 30 is appropriately shortened.

Unitary multi-polar ferrule or cover 10 of FIGS. 3, 4 or 5 may bereplaced with a plurality of separate ferrules that are disposed in andattached to a corresponding cover, substrate, container or shield. FIG.4 shows inner braze joint 65, intermediate braze joint 15, outer brazejoint 40, inner solder joint 55 and outer adhesive joint 45 of thepresent invention. It will now become apparent to those skilled in theart that many other embodiments and configurations of uni-polar andmulti-polar feedthrough assemblies fall within the scope of the presentinvention, including those where inner solder joint 55 is replaced withor augmented by inner adhesive joint 55, outer adhesive joint 45augments or is replaced by outer solder joint 45, and/or outer brazejoint 40 is eliminated.

FIG. 6 shows a perspective, cut-away view of the internal components ofone embodiment of implantable medical device 70 of the presentinvention. In FIG. 6, a generic implantable pulse generator (or IPG) 70is shown. IPG 70 includes battery section 101, hybrid electronicssection or internal circuitry 75, and feedthrough assembly 5, allenclosed by can, shield or container 20. Conductor materials forfeedthrough assemblies 5 are most preferably selected on the basis oftheir reported stability when in contact with body fluids. Feedthroughassembly may comprise one or more feedthroughs, and provides a hermeticseal for device 70. FIG. 7 shows a cross-sectional view of theimplantable medical device of FIG. 6.

In one adhesive application step of the present invention, theelectrically conductive adhesive materials employed to form adhesivejoints 47 and/or 57 must be heated to a temperature that most preferablydoes not exceed about 200 degrees Celsius to cure the adhesives aftertheir application. A preferred curing temperature for ABLEBOND 8700Eadhesive has been found to be about 175 degrees Celsius for a durationof about 1 hour. Maximum curing temperatures for suitable adhesives ofthe present invention are less than about 500 degrees Celsius andgreater than about 15 degrees Celsius. A preferred range of adhesivecuring temperatures of the present invention is between about roomtemperature and about 250 degrees Celsius. A preferred range of adhesivecuring times or durations of the present invention is between about 1minute and about 24 hours.

In a preferred method of the present invention, the adhesive applicationstep occurs at room temperature, where feedthrough assembly 5 is held atroom temperature while a suitable adhesive is applied to inner brazejoint 65 and outer braze joint 45. Assembly 5 is then cured at elevatedtemperatures of about 175 degrees Celsius for about one hour, mostpreferably in a Model No. OV-12A oven provided by Blue M ElectricCompany of Blue Island, Ill.

In one brazing step of the present invention, the metals or alloysemployed to form braze joints 15, 40 and 65 must be heated to atemperature exceeding about 500 degrees Celsius. In a preferred methodof the present invention, the brazing step occurs at peak temperaturesof about 1,090 degrees Celsius, where feedthrough assembly 5 is held andsoaked at that peak temperature for about 40 seconds following apreferred heating ramp-up period of about 1 hour during which timeassembly 5 is taken from room temperature to the peak temperature.Additionally, it is preferred that assembly 5 be pre-soaked at atemperature of about 1,050 degrees Celsius for about 2 minutes tostabilize temperatures throughout the brazing furnace and graphitefixture within which assembly 5 is held during the brazing step.

A preferred cooling ramp-down period following the peak temperaturebrazing period is also about one hour. Preferred ramp-up and ramp-downperiods of the brazing step of the method of the present invention rangebetween about 20 minutes and about 6 hours. The peak temperature of thebrazing step of the method of the present invention is most preferablyabout 50 degrees Celsius above the melting temperature of the brazingmetal or alloy selected, but may range as low as the melting temperatureof the brazing metal or alloy selected.

A preferred furnace for the brazing step of the present invention is aModel No. 3040 WORKHORSE® furnace manufactured by VACUUM INDUSTRIES® ofSommerville, Mass. It is preferred that the brazing step of the presentinvention occur in a vacuum or inert atmosphere. If a vacuum is employedin the brazing step, pressures less than about 8×10⁻⁵ Torr are preferredprior to initiating brazing. Much less preferably, and owing to theresultant excessive oxidation of the pin and ferrule, the brazing stepof the present invention may occur in air or other non-inert atmosphere.

In a preferred method of the present invention, the soldering stepoccurs at peak temperatures of about 275 degrees Celsius, wherefeedthrough assembly 5 is held at that peak temperature for about 30seconds following a preferred heating ramp-up period of about 5 minutesduring which time assembly 5 is taken from room temperature to the peaktemperature. Preferred ramp-up and ramp-down rates are about 5 degreesper second. A resistance heating soldering method is preferred in thepresent invention.

Prior to initiating soldering, it is preferred that air be removed fromthe solder chamber by a combined vacuum-backfill-exhaust procedure.First, a vacuum of about 30 inches mercury is achieved. Then the chamberis backfilled with nitrogen until a pressure of about 10 psig isattained. Finally, nitrogen gas is withdrawn from the chamber untilatmospheric or ambient pressures are attained. Next, the foregoingvacuum-backfill-exhaust procedure is repeated several times, followed bythe chamber being filled with nitrogen, the nitrogen being expelleduntil a pressure of about 5 psig is attained, and the chamber being heldat that pressure.

A preferred cooling ramp-down period following the peak temperaturesoldering period is also about 5 minutes. Preferred ramp-up andramp-down periods of the soldering step of the method of the presentinvention may range between about 20 seconds and about 10 minutes. Thepeak temperature of the soldering step of the method of the presentinvention is most preferably about 75 degrees Celsius above the meltingtemperature of the soldering metal or alloy selected, but may range aslow as the melting temperature of the soldering metal or alloy selected.

A preferred furnace for the soldering step of the present invention is aModel DAP 2200 furnace manufactured by SCIENTIFIC SEALING, INC.® ofDowney, Calif. It is preferred that the soldering step of the presentinvention occur in a vacuum, a nitrogen atmosphere or other inertatmosphere. Less preferably, and providing flux is employed in thesoldering step, the soldering step of the present invention may occur inair or other non-inert atmosphere.

FIG. 8 shows a flow chart of one method of the present invention. InFIG. 8, ferrule or cover 10, pin 30, insulator 25, and braze jointpre-forms corresponding to inner braze joint 65, intermediate brazejoint 15 and outer braze joint 40 are provided. The foregoing componentsare assembled in a braze fixture, most preferably in a graphite brazefixture. Next, assembled ferrule or cover 10, pin 30, insulator 25, andbraze joint pre-forms corresponding to element 65 of the Figures,intermediate braze joint 15 and outer braze joint 40 are heated to anappropriate brazing temperature exceeding about 500 degrees Celsius in abrazing step to form a brazed feedthrough assembly.

Following the brazing step, at least one metal layer is disposed ininner surface 75 and outer surface 80 of capacitive filter 50 tofacilitate attachment of capacitive filter 50 to outer adhesive joint 47and/or outer solder joint 45 on the one hand, and inner adhesive joint57 and/or inner solder joint 55 on the other hand. In a preferred methodof the present invention, a first nickel layer and a second gold layerare sputtered successively onto thick films overlying inner surface 75and outer surface 80.

Next, inner braze joint 65 and outer braze joint 40 are sputteredsuccessively with a first layer of titanium, a second layer nickel and athird layer of gold. Capacitive filter 50, an inner solder joint preformcorresponding to element 55 of the Figures and contact pad 60 are placedon or in the brazed feedthrough assembly, whereupon the so-combinedfeedthrough assembly is heated to a temperature less than about 500degrees Celsius, most preferably in accordance with the methods andparameters described hereinabove respective soldering. In another methodof the present invention, capacitive filter 50 and an outer solder jointpreform corresponding to element 45 are placed on or in the brazedfeedthrough assembly, whereupon the so-combined feedthrough assembly isheated to a temperature less than about 500 degrees Celsius, mostpreferably in accordance with the methods and parameters describedhereinabove respective soldering.

A suitable electrically conductive adhesive may be applied in thirdaperture 35, which upon subsequent curing forms inner adhesive joint 55.Depending upon the structural configuration selected, the same or adifferent suitable electrically conductive adhesive may also be appliedbetween outer braze joint 40 and outer surface 80 of capacitor 50, whichupon subsequent curing forms outer adhesive joint 45. (In another methodof the present invention, the same or a different suitable electricallyconductive adhesive may be applied between intermediate braze joint 15and outer surface 80 of capacitor 50, which upon subsequent curing formsouter adhesive joint 45.) The foregoing components, adhesives and brazedassembly are heated to an appropriate temperature, typically less thanor equal to about 200 degrees Celsius in an adhesive curing step.

In the present invention, it has been discovered that under mostcircumstances it is difficult to apply a continuous, unbroken bead ofadhesive between outer braze joint 40 and outer surface 80. Moreover,leaktightness testing of intermediate braze joint 15 may be compromisedif a continuous bead of adhesive is employed to form adhesive joint 45.(Such a continuous bead might indicate leaktightness even though brazejoint 15 is not leaktight.) For the foregoing reasons, and asillustrated in FIG. 2 hereof, adhesive joint 45 is most preferablyformed by a plurality of adjoining strips or portions of adhesive. Inlike fashion, inner adhesive joint 55 may be formed from a plurality ofadjoining strips or portions of adhesive.

FIG. 9 shows a graph of EMI insertion loss data obtained with capacitivefilter feedthroughs of the present invention disposed withinconventional pacemakers. FIG. 9 shows test results obtained employingone embodiment of the present invention, where a capacitive filterfeedthrough contained gold braze joints or pads 15, 40 and 65 incombination with adhesive joint 45 and inner solder joint 55.

Insertion loss is a measurement of the attenuation of unwanted signalssuch as EMI. Insertion loss was measured using a spectrum analyzer thatgenerated ac signals having frequencies ranging between 0 and 2.9Gigahertz. Analyzer output signals were applied to feedthrough pins 30by a first cable. The analyzer received input signals through a secondcable connected to contact pad 60. We define insertion loss here as:##EQU1## where: E₁ =output voltage with feedthrough in the circuit

E₂ =output voltage with feedthrough not in the circuit

The insertion loss curves of FIG. 9 were generated by sweeping testfrequencies between 0 and 2.9 Gigahertz and simultaneously measuringinsertion loss. FIG. 9 shows that feedthrough assemblies of the presentinvention attenuate EMI significantly.

Although only a few exemplary embodiments of the present invention havebeen described in detail above, those skilled in the art will appreciatereadily that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of the invention. Accordingly, all such modifications areintended to be included within the scope of the present invention asdefined in the following claims. For example, any one of inner adhesivejoint 55, outer adhesive joint 45, intermediate braze joint 15, innerbraze joint 65, outer braze joint 40, inner solder joint 55 or outersolder joint 45 of the present invention may be replaced with a suitableelectrically conductive plastic or polymer containing or blended withsilver flakes or a suitable electrically conductive epoxy or filler. Or,any of the various possible combinations that may be formed by combiningtwo or more of inner adhesive joint 55, outer adhesive joint 45,intermediate braze joint 15, inner braze joint 65, outer braze joint 40,inner solder joint 55 and outer solder joint 45 may be employed in thepresent invention.

The scope of the present invention is not limited to pacing, monitoringor sensing applications, but extends to defibrillation, cardiac mappingand other medical and medical device applications and methods. The scopeof the present invention is not limited to applications where a humanheart is sensed, monitored, paced, or defibrillated, but includessimilar applications in other mammalians and mammalian organs.

The preceding specific embodiments are illustrative of the practice ofthe invention. It is to be understood, therefore, that other expedientsknown to those skilled in the art or disclosed herein, may be employedwithout departing from the invention or the scope of the appendedclaims.

In the claims, means-plus-function clauses are intended to cover thestructures described herein as performing the recited function and notonly structural equivalents but also equivalent structures. Thus,although a nail and a screw may not be structural equivalents in that anail employs a cylindrical surface to secure wooden parts together,whereas a screw employs a helical surface, in the environment offastening wooden parts a nail and a screw are equivalent structures.

All patents listed in Table 1 or elsewhere hereinabove are herebyincorporated by reference into the specification hereof, each in itsrespective entirety.

We claim:
 1. A feedthrough assembly for an implantable medical device,comprising:(a) an electrically conductive ferrule having a firstaperture disposed therethrough, the first aperture having firstsidewalls; the ferrule being formed of at least one of titanium,niobium, platinum, molybdenum, zirconium, tantalum, vanadium, tungsten,iridium, rhodium, rhenium, osmium, ruthenium, palladium, silver, andalloys, mixtures and combinations thereof; (b) an insulator having asecond aperture disposed therethrough, the second aperture having secondsidewalls, the insulator being disposed within the first aperture andbeing formed of a ceramic-containing, electrically insulative material;(c) an electrically conductive pin having upper and lower portions, atleast the upper portion of the pin extending into the second aperture,the pin being formed of at least one of titanium, niobium, platinum,molybdenum, zirconium, tantalum, vanadium, tungsten, iridium, rhodium,rhenium, osmium, ruthenium, palladium, silver, and alloys, mixtures andcombinations thereof; (d) an electrically conductive inner braze jointdisposed atop the upper portion of the pin or between the pin and thesecond sidewalls of the second aperture, to form a seal therebetween,the inner braze joint being formed of at least one of: (1) pure gold;(2) a gold alloy comprising gold and at least one of titanium, niobium,vanadium, nickel, molybdenum, platinum, palladium, ruthenium, silver,rhodium, osmium, iridium, and alloys, mixtures and thereof; (3) acopper-silver alloy comprising copper, silver and optionally at leastone of iridium, titanium, tin, gallium, palladium, platinum, and alloys,mixtures and combinations thereof; and (4) a silver-palladium-galliumalloy; (e) an electrically conductive intermediate braze joint disposedbetween the insulator and the first sidewalls of the first aperture toform a seal therebetween, the intermediate braze joint being formed ofone or more of: (1) pure gold; (2) a gold alloy comprising gold and atleast one of titanium, niobium, vanadium, nickel, molybdenum, platinum,palladium, ruthenium, silver, rhodium, osmium, iridium, and alloys,mixtures and thereof; (3) a copper-silver alloy comprising copper,silver and optionally at least one of iridium, titanium, tin, gallium,palladium, platinum, and alloys, mixtures and combinations thereof; and(4) a silver-palladium-gallium alloy; (f) a ceramic-containingcapacitive filter having one of a third aperture and a passagewaydisposed therethrough, a first electrical terminal being disposedwithin, contiguous with or propinquant to the third aperture orpassageway, a second electrical terminal being disposed on orpropinquant to an outer surface of the capacitive filter; (g) anelectrically conductive inner adhesive joint or inner solder jointdisposed within the third aperture or the passageway, the inner adhesivejoint or inner solder joint being electrically and mechanicallyconnected to the inner braze joint or the first terminal, the innersolder joint being formed of at least one of: (1) an indium-lead alloy;(2) indium only; (3) lead only; (4) silver only; (5) tin only; (6) anindium-silver alloy; (7) an indium-tin alloy; (8) a tin-lead alloy; (9)a tin-silver alloy; (10) an indium-lead-silver alloy; (11) atin-lead-silver alloy; (12) a gold-tin alloy; (13) a gold-silicon alloy;(14) a gold-germanium alloy; and (15) a gold-indium alloy, and (I) anelectrically conductive outer adhesive joint or outer solder jointdisposed between the ferrule and the second electrical terminal, theouter adhesive joint or outer solder joint electrically and mechanicallyconnecting the ferrule to the second terminal, the outer solder jointbeing formed of at least one of: (1) an indium-lead alloy; (2) indiumonly; (3) lead only; (4) silver only; (5) tin only; (6) an indium-silveralloy; (7) an indium-tin alloy; (8) a tin-lead alloy; (9) a tin-silveralloy; (10) an indium-lead-silver alloy; (11) a tin-lead-silver alloy;(12) a gold-tin alloy; (13) a gold-silicon alloy; (14) a gold-germaniumalloy; and (15) a gold-indium alloy; wherein the capacitive filter, incombination with the electrical connections established to the first andsecond terminals thereof from, respectively, the pin and the ferrule,attenuates electromagnetic interference when installed in an implantablemedical device.
 2. The feedthrough assembly of claim 1, wherein anelectrically conductive outer braze joint is disposed between theferrule and the outer surface of the capacitive filter, the outer brazejoint being formed of at least one of: (1) pure gold; (2) a gold alloycomprising gold and at least one of titanium, niobium, vanadium, nickel,molybdenum, platinum, palladium, ruthenium, silver, rhodium, osmium,iridium, and alloys, mixtures and thereof; (3) a copper-silver alloycomprising copper, silver and optionally at least one of iridium,titanium, tin, gallium, palladium, platinum, and alloys, mixtures andcombinations thereof; and (4) a silver-palladium-gallium alloy.
 3. Thefeedthrough assembly of claim 1, wherein the capacitive filter isdisposed at least partially in the first aperture.
 4. The feedthroughassembly of claim 1, wherein a lower surface of an electricallyconductive contact pad is electrically and mechanically connected to theinner adhesive joint or inner solder joint, the contact pad having anupper surface suitable for wirebonding, soldering, gluing, welding,laser welding, or brazing an electrical connection thereon or thereto.5. The feedthrough assembly of claim 4, wherein the contact pad isformed of one of: (a) having first a layer of nickel and then a layer ofgold disposed on the surface thereof; (b) brass having first a layer ofnickel and then layer of gold disposed on the surface thereof; (c) puregold; (d) nickel having a layer of gold disposed on the surface thereof,and (e) pure copper or copper alloy having first a layer of nickel andthen a layer of gold disposed on the surface thereof.
 6. The feedthroughassembly of claim 4, wherein the contact pad is electrically connectedto internal circuitry disposed within an implantable medical device. 7.The feedthrough assembly of claim 1, wherein an hermetic seal isprovided between the ferrule and the capacitive filter by at least oneof the outer braze joint, the outer adhesive joint or the outer solderjoint.
 8. The feedthrough assembly of claim 1, wherein an hermetic sealis provided between the insulator and the pin by at least one of theinner braze joint, the inner adhesive joint or the inner solder joint.9. The feedthrough assembly of claim 1, wherein a hermetic seal isprovided between the insulator and the first aperture by theintermediate braze joint.
 10. The feedthrough assembly of claim 1,wherein the ferrule is electrically and mechanically connected to one ofa housing, container, cover, and shield in an implantable medicaldevice.
 11. The feedthrough assembly of claim 1, wherein the ferruleforms a portion of, and is structurally unitary in respect of, one of ahousing, container, cover, case and shield in an implantable medicaldevice.
 12. The feedthrough assembly of claim 1, wherein the implantablemedical device is one of a pacemaker, an implantable pulse generator, adefibrillator, a pacemaker-cardioverter-defibrillator, a neurologicalstimulator and a gastro-intestinal stimulator.
 13. The feedthroughassembly of claim 1, wherein the pin is electrically connected to one ofa connector block and a connector located outside the implantablemedical device.
 14. The feedthrough assembly of claim 1, wherein thecapacitive filter is a discoidal capacitor.
 15. The feedthrough assemblyof claim 1, wherein the capacitive filter is a multi-layer capacitor.16. The feedthrough assembly of claim 1, wherein the capacitive filtercomprises barium titanate.
 17. The feedthrough assembly of claim 1,wherein the capacitive filter is selected from the group consisting ofsingle-layer capacitors, rectangular capacitors, square capacitors,elliptical capacitors, and oval capacitors.
 18. The feedthrough assemblyof claim 1, wherein the capacitive filter has at least one of a silverthick film, a silver-palladium alloy thick film, and a silver-platinumalloy thick film disposed on the inner capacitive filter surface orouter capacitive filter surface thereof.
 19. The feedthrough assembly ofclaim 17, wherein the capacitive filter has at least one nickel or goldlayer sputtered onto the thick film surfaces thereof.
 20. Thefeedthrough assembly of claim 1, wherein at least one of niobium,titanium, titanium-tungsten alloy, tungsten and molybdenum are sputteredonto an inner surface or an outer surface of the insulator.
 21. Afeedthrough assembly for an implantable medical device, comprising:(a)means for forming an electrically conductive ferrule having a firstaperture disposed therethrough, the first aperture having firstsidewalls; (b) means for insulating having a second aperture disposedtherethrough, the second aperture having second sidewalls, theinsulating means being disposed within the first aperture and beingformed of a ceramic-containing, electrically insulative material; (c)means for forming an electrically conductive pin having upper and lowerportions, at least the upper portion of the pin forming means extendinginto the second aperture; (d) means for forming an electricallyconductive inner braze joint disposed atop the top portion of the pinmeans and between the pin forming means and the second sidewalls of thesecond aperture to form a seal therebetween; (e) means for forming anelectrically conductive intermediate braze joint disposed between theinsulating means and the first sidewalls of the first aperture to form aseal therebetween; (f) a means for capacitively filtering having one ofa third aperture and a passageway disposed therethrough, a firstelectrical terminal being disposed within or propinquant to the thirdaperture or passageway, a second electrical terminal being disposed onan outer surface of the capacitive filtering means; (g) means forforming an electrically conductive inner adhesive joint or inner solderjoint disposed within or propinquant to the third aperture or thepassageway, the inner adhesive or solder joint forming means beingelectrically and mechanically connected to the inner braze joint formingmeans or the first terminal; (h) an electrically conductive means forforming an outer adhesive joint or an outer solder joint disposedbetween the ferrule forming means and the second electrical terminal,the outer adhesive or solder joint forming means electrically andmechanically connecting the ferrule forming means and the secondterminal; wherein the capacitive filtering means, in combination withthe electrical connections established to the first and second terminalsthereof from, respectively, the pin forming means and the ferruleforming means, attenuates electromagnetic interference when installed inan implantable medical device.
 22. The feedthrough assembly formingmeans of claim 21, wherein an electrically conductive means for formingan outer braze joint is disposed between the ferrule and the outersurface of the capacitive filtering means.